Knowledge that Transforms

What is the weak-instruments (WI) problem and what causes it? Universal agreement does not exist on these questions. We define weak instruments by two features: (i) two-stage least squares (2SLS) analysis is badly biased toward the ordinary least-squares (OLS) estimate, and alternative “unbiased” estimators such as limited-information maximum likelihood (LIML) may not solve the problem; and (ii) the standard (first-order) asymptotic distribution does not give an accurate framework for inference. Thus, a researcher may estimate “bad results” and not be aware of the outcome. The cause of WI is often stated to be a low R or F statistic of the reduced-form equation, in the most commonly occurring situation of one right-handside endogenous variable. We find the situation is more complex with an additional factor, the correlation between the stochastic disturbances of the structural equation and the reduced form, that needs to be taken into account. We discuss in this paper a specification test (Hahn and Hausman, 2002a) for WI, a caution against using “no moments” estimators such as LIML in the WI situation, and suggestions for different estimators, an approach to inference of Frank Kleibergen (2002) for WI. We end with a caution of how “small biases” can become “large biases” in the WI situation. We begin with the limited-information structural model under the assumptions of Hausman (1983):

This paper studies a model of random technical progress where technology diffuses at realistically slow rates. It fits smooth trends to the sum of GDP series generated by this model and series representing transitory, or cyclical, fluctuations. Detrended GDP is then largely unrelated to technical progress. The detrending method proposed by Rotemberg (1999) reconstructs cyclical variations somewhat more accurately than the HP filter. With sufficiently slow diffusion it is also more accurate than a method based on VARs fitted to hours and GDP growth. Consistent with the model’s predictions, permanent shocks initially depress both hours and output in these VARs.

This paper provides an analytical characterization of Markov perfect equilibria in a model with repeated voting, where agents vote over distortionary income redistribution. A key result is that the future constituency for redistributive policies depends positively on current redistribution, since this affects both private investments and the future distribution of voters. The model features multiple equilibria. In some equilibria, positive redistribution persists forever. In other equilibria, even a majority of beneficiaries of redistribution vote strategically so as to induce the end of the welfare state next period. Skill-biased technical change makes the survival of the welfare state less likely.

We consider monetary-fiscal interactions when the monetary authority is more conservative than the fiscal. With both policies discretionary, (1) Nash equilibrium yields lower output and higher price than the ideal points of both authorities, (2) of the two leadership possibilities, fiscal leadership is generally better. With fiscal discretion, monetary commitment yields the same outcome as discretionary monetary leadership for all realizations of shocks. But fiscal commitment is not similarly negated by monetary discretion. Second-best outcomes require either joint commitment, or identical targets for the two authorities—output socially optimal and price level appropriately conservative—or complete separation of tasks.

Monetary and Nonmonetary Punishment in the Voluntary Contributions Mechanism by David Masclet, Charles Noussair, Steven Tucker and Marie-Claire Villeval. Published in volume 93, issue 1, pages 366-380 of American Economic Review, March 2003

This paper considers a dynamic model of innovations in which firms can endogenously bias the direction of technological change. Both in a North–North and North–South context, we show that, when globalization triggers an increased threat of technological leapfrogging or imitation, firms tend to respond to that threat by biasing the direction of their innovations towards skilled-labor-intensive technologies. We show that this process of defensive skill-biased innovations generates an increase in wage inequalities in both regions. We then discuss suggestive empirical evidence of the existence of defensive skill-biased technical change.

Historically, the average return on S&P stocks has far exceeded the average return on short-term U.S. government debt. Rajnish Mehra and Prescott (1985), for example, found that the average difference was 6.2 percent per year in the 1889–1978 period. They tried to account for this difference by assuming it is a premium for bearing nondiversi � able aggregate risk but found that risk accounted for only a tiny fraction of the difference. They concluded that there is an “equity premium puzzle.” Here, we reexamine this puzzle, taking into account some factors ignored by Mehra and Prescott (taxes, regulatory constraints, and diversi� cation costs) and focusing on long-term

Global aging is prompting workers and taxpayers everywhere to recognize their vulnerability to the inherent uncertainty of unfunded social-security systems. This has generated an international wave of social-security reforms over the last two decades, prompting more than 20 countries to establish Individual Account (IA) plans. In the United States, the idea of Individual Accounts has attracted recent interest with the release of the Final Report of the President's Commission to Strengthen Social Security (CSSS): here, voluntary individual accounts were proposed as a key element of a reformed national old-age system (see Commission to Strengthen Social Security, 2001; John F. Cogan and Mitchell, 2003). Strengths of IA's include the fact that participants gain ownership in their accounts and diversify their pension investments; nevertheless, IA participants also must bear capital-market risk. Recent market volatility has reminded investors of the importance of capital-market fluctuations and their potential impact on retirement income. In response, some policymakers have suggested that "guarantees" be designed to help protect IA investments. Abroad, such guarantees have been adopted in several Latin American countries undergoing reform, and most recently, in Japan and Germany (Mitchell and Kent Smetters, 2003). Sensible public policy recommending the adoption of guarantees must identify their costs and who will pay for them. In this paper, we discuss how to evaluate such costs in the context of a social-security reform that includes IA's, along with ways to finance them.

Forms of Intolerance held in early September 2001 was unfortunately obscured by the tragic events of September 11. Nonetheless, the event reflects global recognition of problems of racial, ethnic and cultural discrimination, oppression and exploitation. The following analysis, inspired by participation in collaborative international research presented to the Conference, suggests that economic discrimination may be usefully seen in terms of rents and rent-seeking. By successfully discriminating against a particular group, employers or consumers succeed in extracting rents from the group discriminate against. However, such rents are different in nature. Discriminated employees (e.g. Blacks) receive lower remuneration or inferior terms of employment. Successful discrimination allows employers to use their availability to extract additional ‘producer surplus ’ by conceding lower (‘intermediate’-level) wages or employment conditions to ostensibly privileged employees (e.g. Whites), than might be the case in the absence of discrimination. Even if there is an eventual equalization of wage rates or employment conditions between the group discriminated against and the privileged group, a ‘producer surplus ’ from the poorer wages or employment conditions may well persist

In this paper we do two things. First we document that over the last 40 years the U.S. business cycle has become less synchronized with the cycle in the rest of the world. Second we try to explain why this has happened. We use a general-equilibrium model as a tool to discriminate between two alternative explanations: (i) a change in the nature of real shocks, and (ii) an increase in U.S. financial integration with the rest of the world. Our results indicate that financial integration has played the major role in producing the observed changes in international co-movement.